Spray generating apparatus



July 14, 1942.

F. W. OFELDT SPRAY GENERATING APPARATUS Filed Feb. 24, 1939 3 Sheets-Shgt 1 July 14, 1942. F. w. OFELDT SPRAY GENERATING APPARATUS Filed Feb. 24, 1939 5 Sheets-Sheet 2 ATTORNEY.

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mvw igmwa 3 Sheets-Sheet 5 Filed Feb. 24, 1939 ATTORNEY.

Patented July 14, 1942 SPRAY GENERATING APPARATUS Frank-W. Ofeldt, McKeesport, Pa., asslgnor to Homestead Valve Manufacturing Company, Coraopolis, Pa., a corporation oi. Pennsylvania Application February 24, 1939, Serial No. 258,199

15 Claims.

This invention relates to spray generation and particularly to methods and apparatus for controlling the generation of a spray composed of a mixture of liquid and a vapor of a liquid under pressure produced by heat. I

This invention may be advantageously applied for cleaning and agriculture spraying wherein solutions of soap and similar cleaning compounds are used or germicides for the impregnation of soil, the spraying of trees and other vegetation. Other applications require liquids peculiar to the requirement of the use including different chemicals, oils and refined products thereof. When aqueous solutions are used the heat is employed for the generation of steam which provides the propulsion of the liquid and when other solutions are employed the vapor pressure generated is used for the same purpose.

Spray generating apparatus of this character are disclosed in Letters Patent Nos. 1,855,866; 1,925,457; 1,925,643; 1,970,971; 2,062,925, and 2,128,263 issued to the present inventor. In spray generating apparatus of this type the pressure is produced by turning a part of the liquid into vapor or steam for atomizing the liquid and the amount of vapor or steam generated is determined by the amount of heat supplied as correlated with the amount of liquid supplied to the apparatus. The proportions of steam to liquid may he changed by varying the amount of either the liquid or the heat supplied per unit of time. Thus the greater the amount of heat the drier the spray and contra'the wetter the spray within the limits of the range of the apparatus in the latent heat zone.

With the use of the controls disclosed in the patents mentioned above the proportion of steam to the liquid may be varied at a substantially constant pressure. In the disclosures of Patents Nos. 1,855,866; 1,925,643 and 1,925,457 the control is operated by the pressure of the mixture for varying the rate of feeding both the liquid and the fuel simultaneously to the heating zone. When the machine started liquid and fuel are simultaneously fed to the heating zone at a rate which builds up to a maximum and then tapers off normally until the liquid is heated suiiiciently to form a mixture within the latent heat zone to produce the desired predetermined pressure. Th s pressure then becomes effective in controlling the feeding apparatus to simultaneously reduce the rate of the liquid and the fuel which results in slight decrease in pressure. The decreased pressure in turn causes an increase in the rate of feeding the liquid and fuel. Thus curves illustrating the rate of feeding the liquid and the fuel are in step and the pressure curve lags slightly and is modulated with respect to the predetermined pressure set by the controls. The magnitude of these curves depend upon the sensitiveness of the structure in response to slight pressure variations. If the nozzle is shut off the pressure is substantially maintained but the liquid and fuel cease to be pumped to the apparatus. When the nozzle is opened the pressure drops quickly but is checked by the resumption of the feeding of liquid and fuel to the heating zone in the same manner. The supply of fuel and liquid in the machines of these disclosures may be varied independently by manually moving the position of the respective pump along the actuating lever arm.

In the disclosures of Patents 1,970,971; 2,062,925, and 2,128,263 the control is operated either by the temperatureor by the pressure of the mixture which is reflective in maintaining a substantially constant pressure by completely stopping and starting the supply of liquid and fuel to the apparatus which when running art fed at definite and exact rates and never change. This may be easily accomplished by the use of a control switch operated by the temperature or pressure of the mixture for energizing an electric motor which drives the liquid and fuel pumps. This type of apparatus employs upper and lower pressure limits, the average of which is the pressure desired. When the machine is started thefuel and liquid are fed at a constant rate while the pressure of the mixtine builds up to a predetermined maximum, causing the pressure control to function, shutting off the supply of fuel and liquid. The spray still functions but the pressure falls to a predetermined minimum, then the control again functions to start the motor and feed fuel and liquid to the apparatus in definite metered quantities per unit of time.

' The differential in these limiting control pres- The pressure is again built up by the feeding of the liquid and the fuel to the heating zone. Since these machines normally operate in the latent heat zone the temperature and pressure on the mixture are functions of each other.

However the liquid in the apparatus at times is in its solid phase, at which time the temperature and pressure are not functions of one another and the thermostatic control is not ef fective for maintaining a constant pressure on the liquid. Thus it is more important to maintain the pressure of the liquid constant regardless of its temperature,

The principal object of the present invention is the provision of a control for maintaining a substantially constant pressure of the mixture by varying the rate of supplying heat to the heating zone of the apparatus which is supplied with liquid metered at a definite and exact rate.

In this control the heat and liquid are supplied to the apparatus until the predetermined operating pressure is generated which in turn is effective in slightly reducing the rate that the heat is supplied to the apparatus. This action produces a slight reduction of pressure in the mixture which then becomes efiective to increase the supply of heat. thereby increasing the vapor pressure of the mixture at a point where it again reduces the rate of supplying the heat. This slight oscillation of the pressure maintains a substantially constant pressure condition in the apparatus. A curve illustrating the fluctuations of the rate of feeding the fuel slightly leads the pressure fluctuations in the amount which is a measure of the sensitivity of the control and which represents another important advantage of this invention.

When the nozzle is shut oii the pressure of the mixture rapidly builds up due to the hydrostatic pressure developed by the constant supply of liquid to the apparatus and the heat is correspondingly cut off by this increase in pressure. About the time the heat is completely out off the liquid fed to the apparatus is being decreased, which continues until it is completely shut off, at which time the maximum hydrostatic pressure is reached in the apparatus. Thus the control of a constant flow of liquid and variable supply of heat governed by the pressure control valve represents another important object of this invention.

When the nozzle is again opened the pressure in the apparatus is momentarily relieved which first reestablishes the constant supply of heat, the fuel pressure then starts to build up, initiating a corresponding supply of heat to the apparatus until the operating pressure is reached, after which the rate of fuel supply is regulated by the oscillations of the pressure as before. This reestablished control also represents another novel advantage representing an object of the present invention.

Another object is the provision of a novel pressure control valve for regulating the heat supply to produce a predetermined pressure in the mixture.

Another object is the provision of a pressure control valve for stopping and starting the feeding of liquid to the apparatus.

Another object is the provision of a spray apparatus having a pressure control valve for regulating the fuel used to heat a liquid fed to the apparatus at a substantially constant rate and for stopping and starting the supply of said liquid when it is subjected to a predetermined pressure.

In spray generation by heat the best results and the most economical operation of the apparatus are obtained when just enough heat is supplied to the constantly flowing liquid passing through the apparatus to Just maintain the desired mixture pressure. Under these conditions the least amount of vapor or steam is generated for the proper functioning of the apparatus and the greatest amount of liquid is discharged which provides the best condition for cleaning purposes.

When aqueous solutions are employed the pressure obtained by the generation of steam may be used to control the supply ofheat to the apparatus and in this manner the greatest amount of liquid in the steam and liquid mixture may be maintained at the pressure carried.

Another advantage obtained by this method of controlling the supplied heat lies in the fact that one is enabled to maintain a constant proportion of the steam and liquid mixture which may be obtained regardless of whether the liquid is preheated before entering the heating zone. Thus the liquid supply tank may surround the combustion chamber as shown and the liquid may be preheated beneficially. Again the ambient temperature has no' effect on the function of the apparatus or the controls, which is an important advantage in spray generation.

When the apparatus is started the liquid in the supply tank may be cold and as the apparatus continues to operate the temperature of the liquid in this tank increases due to the radiation of heat from the combustion zone. The temperature of this liquid increases until a'heat balance is obtained. that is the supply of cold liquid to the tank absorbs the heat by radiation and the temperature of the liquid in the tank remains substantially constant.

It is apparent that the preheating of the liquid in this manner reduces the B. T. U. requirement in the heating zone to produce the proper proportions of liquid and steam in the mixture. Thus by controlling the supply of heat by means of the pressure of the mixture with a constant supply of liquid to the apparatus a heat balance is obtained which provides economic operation of the spray generator which represents an important object of this invention and insures constant operating pressures regardless of temperature of the liquid.

Other objects will be apparent from the following description and claims.

In the accompanying drawings which illustrate the practical embodiments of the spray generating apparatus which comprise the prin-- ciples of this invention and wherein the liquid fuel i employed as the heating medium:

Fig, l is a diagrammatic View showing a spray generating apparatus employing an atomizing type burner.

Fig. 2 is a diagrammatic view showing a spray generating apparatus employing a vaporizing type burner.

Fig. 3 is a diagrammatic view showing apparatus similar to that illustrated in Fig. 2 showing a modified control.

Referring to Fig. 1 of the drawings, I0 represents the liquid supply tank which may be provided with the liquid level float valve H connected in this instance through a hose line to the water tap l2. Chemicals may be supplied through the valve II or mixed within the tank by adding them in the proper proportion to the amount of water or other basic liquid used. For the purpose of simplicity it will be assumed that water is employed as the basic liquid for the spray generating apparatus in describing the principles of this improved control, in which case the term vapor should be understood to include steam.

For convenience it will be assumed that oil is employed as fuel and is stored in the tank i3 immersed in the liquid in the tank ill.

The combustion chamber i5 is formed by the horizontally disposed shell l6 and having a verthe coils horizontally each turn thereof forms a trap wherein the liquid, when at rest in adjacent turns, trap-s the generated steam therebetween, preventing it from accumulating with other steam generated in the coil. This improvement is disclosed in Letters Patent No. 2,111,538.

2 The outer end of the combustion chamber is closed by the wall of the tank it! which is provided with a hole for receiving the burner assembly 2| which comprises the burner 22 centrally supported in the blower housing 23 and extending into the combustion chamber. 26 represents a flame guiding ring made of heatresisting steel which encircles the jet of the burner and is supported on the end of the housing 26. A squirrel cage type rotary fan is mounted in the other end of the housing 23, having its vortex-open to and in spaced relation with the wall of the housing forming the air inlet 26. The other end of the fan is closed and is provided with a bored hub for receiving the end of the shaft 21 extending from the pump 26. The other end of the shaft is provided with a pulley 29 arranged to receive the belt 36 which in turn is driven by the electric motor indicated at 3| and provided with a suitable overload switch and cord connection for plugging into a suitable source of power.

62 represents a pair of electrodes mounted on the jet of the burner for igniting the fuel as it issues therefrom. The electrodes are electrically connected to the terminals 33 of the spark coil 66.

The pump 26 is of the positive displacement type disclosed in Letters Patent No. 2,131,749 and is provided with three pistons, two of which work in multiple drawing liquid from the tank It through the pipe 65 and discharging the same through the pipe 36, the heat transfer inlet pipe 3'4, the coils i6 and 26 in multiple, the heat transfer outlet pipe 66, the flexible hose 66 and is discharged out the gun M. A valve ti is provided between the pipe 66 and the hose 36 which may be of considerable length. The gun is also provided with a controlvalve 42 to enable the operator to turn on or shut off the discharge of liquid therefrom.

The third piston in the pump it draws oil from the tank iii through the pipe 63, the strainer it i, and the pipe 66 and delivers it through the pipe 66 to the fuel control valve ll from which it travels through pipe 48 to the jet of the burner assembly 22. The pipe line 66 returns the oil that is by-passed from the valve t'l to the pipe 66 on the suction side of the oil pump.

66 represents the liquid by pass control valve which is provided with two chambers 6| and 62 interconnected through the passageway 63 having an adjustable orifice. These chambers are separately connected to the inlet and outletends of the coils through the pipes 54 and 55 respectively. The'pipe line 56 returns the liquid from the control valve 56 to the tank Ill.

The control valves for the fuel and liquid have their separate functions to perform. However, the liquid control valve 56 also functions as a by-pass of the fuel. Thus it is convenient to incorporate both valves in the common housing made up of the two castings 61 and 58 with the open space 56 formed therebetween for separating the liquid chambers from the fuel chambers.

The fuel is pumped from the tank I6 through the pipe 46 to control valve 41 where it enters.

the chamber 66. When the hydrostatic pressure of the fuel in this chamber reaches a predetermined pressure the spring loaded hollow valve plunger 6| is moved to the left, compressing the spring 62 in the chamber 63 which is connected to the by-pass return line 49. The pressure of the spring 62 thus determines the fuel pressure. The hollow valve plunger 6| is provided with an inturned annular flange having an axial opening through which the stem of the axial valve member 66 extends. The valve 64 is seated by the spring 66 on the valve seat 66 controlling the flow of fuel from the chamber through the pipe 66 to the burner jet. As shown the valve plunger 6| and the spring 65 maintains the valve 66 seated and it does not become unseated until the plunger 6| moves sufficiently to the left -.to take up the lost motion between the head on the stem and the flange on the plunger 6| during which time the cushion spring 65 maintains the valve 66 on its seat 66.

The wall of the valve plunger 6| is provided with the ports 61 for connecting the chambers 66 and 63 when moved to the left. When the hydrostatic pressure is sufficient to move the plunger 6| to the left and'take up the lost motion, the valve 66 becomes unseated and the fuel passes from the chamber 66 to the burner. The pressure required to move this valve may be set initially by the choice of the spring 62, the pressure of which insures proper atomization of the fuel. I

If the fuel in the chamber 66 builds up a higher static pressure the valve 6| will be moved further to the left until the ports 61 by-pass the fuel from the chamber 66 to the chamber 63, whence it is conveyed back to the fuel supply through pipe 46 and the pressure required to open this by-pass represents the maximum fuel pressure attainable.

Again the fuel must reach a definite pressure before it is fed to the jet of the burner and if for any reason the fuel pressure drops below this amount the valve member 64 will immemately seat, thus stopping the how of fuel to the burner. This action prevents smoking when the fuel is cut off and during the starting and stopping of the machine.

The liquid valve 66 comprises a hollow valve plunger 68 having one end in the chamber 52 and the other end in the open space 59. This plunger has a long stem 69 secured to the outer end thereof and is sealed where it -enters the chamber 62 by the hydraulic packing 'l'il compressed by the gland rnember H. The plunger is loaded by the spring ll. which surrounds the stem and the tension of which may be varied by the adjusting nut 76. Since the adjusting nut is threadably engaged with the valve casting 51 and extends into the open space 59 the adjustment of the tension of the spring 12 may be made at any time, thereby effecting a change in the operating pressure of the spray generating machine. The other end of the plunger stem 69 extends through the packing 14 into the chamber 63 where it may engage the ball valve 15 which is held on its seat by the spring 16 and when unseated by-passes the fuel from chamber 60 to chamber 63 and thence by the return pipe 49 to the fuel supply.

The head of the hollow valve plunger 68 is provided with an inturned annular flange forming an axial opening through which the stem of the valve 11 extends. This stem also passes through the partition, dividing the chambers 5i and 52 and the valve face on the endthereof engages the seat 18 for controlling the liquid by-pass return line 56. The valve TI is seated by the helical spring 19 in the plunger and is unseated or picked up by-the plunger 68 after the latter has traveled to the right sufficiently to overcome the lost motion between the enlarged portion on the stem and the inturned annular flange on the plunger.

The operation of the spray generating apparatus is started by the closing of the electric circuit to energize the motor 3i and the spark coil 34 which starts the motor and discharges a spark across the gap of the electrodes 32. Liquid is then drawn from the tank l0, through pipe 35 to the pump 28 where it is forced through pipes 36 and 31, the coils I9 and 20, the pipe 38, valve 4!, the hose 39, and is discharged out of the nozzle of the gun 40. At the same time fuel is drawn from the tank I3, through the pipes 43 and 44 to the pump 28 and is forced through the pipe 46 to the chamber 60 in the valve 47. In a very short space of time the hydrostatic pressure of the fuel in the chamber forces the plunger 6i to the left and when it has moved sufficiently to cover the lost motion the valve 64 is lifted from the seat 66 and the fuel under a predetermined pressure, fixed by the tension of the spring 62 on the plunger 6|, passes on through the pipe 48 to the burner assembly where it is atomized and discharged past the spark between the electrodes 32, which ignites the fuel, into the combustion chamber l5.

The metered liquid in the coils is then heated by a metered quantity of fuel to within the latent heat zone where steam is generated, forming a mixture with the liquid and producing a pressure which is the same in the pipes 31 and 38 at both ends of the coil. This pressure moves the mixture through the system to the gun where it is discharged as a constant spray and is effective through the pipes 54 and 55 in the chambers 5i and 52 of the control valve. As this pressure builds up in the chamber 52 to a value slightly above the normal operating pressure of the apparatus it moves the plunger 68 to the left, overcoming the pressure of the spring 12, and the stem 69 unseats the ball valve Iii, thus by-passing the fuel from the chamber through the chamber 63, the pipe 49 to the source of fuel supply. The opening of the valve 15 decreases the fuel pressure, having the effect of reducing plunger stem 68 again opens the ball valve 15 reducing the fuel pressure.

Thus the liquid is metered by the pump and is forced through the heating zone at a predetermined constant rate while the fuel is varied by the pressure of the mixture to maintain a substantially constant pressure thereon producing a predetermined state or condition. Thus curves charting the pressure of the mixture and the fuel show small oscillation above and below the normal pressure with the mixture pressure curve leading the fuel pressure curve and the oscillations of both being within definite limits.

Thus by maintaining a constant flow of liquid at a predetermined rate to the heating coils and controlling the pressure of the mixture formed by maintaining the required amount of oil for heating this metered liquid the apparatus produces a steam vapor liquid mixture with a constant maximum amount of liquid and a minimum amount of vapor or steam, regardless of the ambient temperature, temperature of the liquid pumped, or heat loss, which has never been attained under these varying factors and is a novel provision of this invention.

During the normal operation of the apparatus as stated above the pressure generated never rises sufiiciently to cause the plunger 68 of the control valve to pick up the valve i1 and open the liquid by-pass which discharges the pumped liquid back into the tank l0. Under normal operation the plunger 68 reciprocates in phase with the pressure oscillations to actuate the oil by-pass valve 15, which movement is within the lost motion between the valve 11 and the inturned annular shoulder of the piston. The sequence of the operation of these by-pass valves produces maximum saturation in the mixture as though the intensity of the fire was varied and a mixture having maximum saturation is superior for cleaning purposes. However if the pressure of the mixture exceeded the normal operating pressure, which is a predetermined amount set by the spring 12, the plunger 68 picks up the valve 11 opening the liquid by-pass and maintains the fuel by-pass valve in its open position, permitting the fuel pressure valve 64 to close, cutting off the fuel to the burner. The plunger 68 is held in this position until the pressure in the coils subsides. The pressure of the mixture exceeds the normal operating pressure when the valve 42 on the spray gun is closed and the pressure control valve 50 then functions as stated above to bypass the fuel and the liquid. The motor continues to operate the pump and if the pressure in the discharge end of the coils falls due to reverse flow through the coils, the pipe 54, the chamber 5|, and out the by-pass line or through the pipe 55, the chamber 52, the passageway 53,

the chamber 5| and out the by-pass line; the

pressure in the chamber 52 decreases allowing the spring 12 to force the plunger 68 to the left. The by-pass valve 11 is the first to close and the liquid, which is continually being pumped, builds up a hydrostatic pressure sufficient to again force the plunger 68 to the right, picking up the valve 11 to again open the liquid by-pass. The fuel bypass valve 15 is held open during this period so no heat is delivered to the coils. In a very short time the pressure control valve reaches a hydrostatic pressure balance, thus permitting the liquid and fuel to circulate through the by-pass lines.

Thus the pressure control valve 50 functions as a by-pass for the liquid and the fuel and also as a relief valve for hydrostatic and thermally generated pressures which also puts it in with the class of safety valves.

The control valve 50 is endowed with other novel features which are necessary to its operation as a practical piece of apparatus. The plunger lid is sealed by the hydraulic packing Ill compressed by the gland it. It is well known that packing of this character has a very high static friction coefficient in comparison to other control devices having metal bellows or diaphragms. But the operating characteristics of such control devices are erratic and they cannot be used in conjunction with high pressures, whereas the plunger he is rugged and can stand high pressures but hereto for this type of apparatus has not been used because it would not respond to slight changes in pressure because of the friction of the packing. This has been overcome in the present invention by subjecting the plunger to hydrostatic impulses, causing it to oscillate continually between relatively short limits. This oscillation of the plunger eliminates the static friction of the packing and any change in pressure on the plunger moves it accordingly as it continues to oscillate. In this instance the pulsations are provided by the reciprocating pistons of the liquid pumps, which pulsations are transmitted through the lines 36 and ti l, the chamber til, the passageway 53, to the chamber 52, where they are effective on the plunger Gil.

Ordinarily the pulsations produced by a reciprocating pump used in apparatus of this type will cause excessive oscillations on. the plunger 68 if directly impressed thereon. An adjustable screw is therefore provided in the passageway to produce a controllable orifice which acts to choke or reduce the pulsations of the liquid in the chamber it to any desired amplitude. These pulsationsare not effective on the discharge side of the heating zone as they are absorbed by the pocketed portions of the vapor or steam; Thus the pipe ht conveys a substantially non-fluctuating pressure of the mixture to the chamber 52 which balances the pressure in the chamber and dampens the pulsations of the liquid which are effective through the passageway 53 for oscillating the plunger lit. if the pulsations are substantially dampened out, the static friction of the packing it makes the piston til move in jerks when subjected to pressure changes and it sharply actuates the fuel valve "it with a snap, avoiding dribbling and smoking of the fuel. The screw valve in the passageway 53 may be eliminated when the pipe connection 55 is made between the chamber ti: and the discharge end of the heating coil provided the passageway 53 is of the proper size for admitting pulsations of sufiicient magnitude which, though dampened by the mixture, oscillate the plunger. However if it is desirable to change the operating pressure and the propertions of the mixture of this machine, it is advantageous to use both the adjustable orifice screw and the pipe line lit to provide accurate adjustment of the oscillating magnitude of the plunger. Each of these adjusting features represent an important advancement in this art. It the pulsations were represented as a curve the oscillations would appear similar to a sine curve with the crests and troughs equidistant above and below the normal pressure line and when superimposed thereon would produce a curve similar to that of an alternating current superimposed on a direct current.

I By adjusting the orifice in the passageway 53 the magnitude of the pulsations, which are effective on the plunger, may be made to oscillate the plunger in phase with the pulsations, thereby keeping it constantly in motion so that any slight change in the pressure of the mixture is immediately eifective to move the plunger to control the fuel and liquid by-pass. By this arrangement a very sluggish acting piston is made into an extremely sensitive control.

Since the fuel pump is also of the reciprocating piston type there are pulsations in the fuel line. However these pulsations are absorbed by the spring loaded plunger M, which acts as a shock absorber or an alleviator, and will oscillate without closing the valve 64. Thus the fuel delivered to the jet of the burner assembly is substantially without pulsations.

The by-pass ports ti in the wall of the plunger ti are positioned to permit the fuel to by-pass if as excessive fuel pressure is developed in the system. Such a pressure may develop by reason that the valve in the burner assembly 22 was left closed or the jet became clogged and thusthe plunger lil would be moved to its extreme position to the left. In this respect the plunger acts as a safety valve for the fuel system.

With this control valve, which is responsive to pressure conditions, the complete operation of the spray generating apparatus is regulated and since the apparatus is operated in the latent heat zone the pressure of the mixture is proportional to the temperature. Thus the temperature and the pressure of the spray mixture is controlled by a simple pressure responsive valve which may be adjusted to produce any desired proportions of liquid and vapor or steam in the spray mixture.

Referring now to Fig. 2 it will be noted that similar parts are shown with the same reference numerals as those used in conjunction with the description of the apparatus shown in Fig 1.

The essential difference between these figures is in the burner assembly. In Fig. 2 the burner assembly til is of the vaporizing type wherein the fuel is drawn from the supply tanlr it through the pipe til, the strainer t l, pipe in to the pump 28; thence through the pipe it to the fuel pressure valve M, the pipe til, the main fuel valve 8!, pipe 32, check valve lit, the vaporizing coil M to the jet nozzle 85. This type of burner is disclosed in Patent No. 2,128,264. A by-pass fuel line 86 with a check valve 8] is connected ahead of the main fuel valve ti for returning a portion of the fuel pumped to the tanlr it.

The liquid is drawn from the tank it through the pipe 35 to the pump it; and is discharged through the pipes in and til, coils in and till in series where it is heated, and through pipe til, hose ti! to the gun til where it is discharged. The

, line M connects the inlet side of the coils to the till! chamber ti of the control valve til and it is not necessary to balance the pressure between the chambers ill and 52 by connections on both sides of the heating coils because the screw in the passageway at for adjusting the orifice to dampen the pulsations is sufficient for this machine since it operates under lower pressure than that disclosed in Fig. 1. The chamber at is plugged as indicated at t'll. However the valves ill and till function in the samemanner as that described with reference to Fig. 1 in controlling the generation of the spray. If this machine is to be operated at a definite pressure all the time then the fixed size passageway 53 is all that would be necessary.

Attention is directed to the fact that the coils i9 and till, one in series and the latter is smaller in diameter and is positioned above the former.

burner.

In Fig. 3 the spray generating apparatus is similar to that disclosed in Fig. 1 except that the fuel pressure valve 41 has been replaced by a modified fuel pressure system which comprises the dual orifice valve 88 in the by-pass line 89 between the pump and the fuel supply. The fuel pump meters the fuel passing therethrough and the valve II is provided with a fixed orifice 90 through the partition thereof. This orifice will permit the escape of a definite proportion of fuel to the supply line I! and since-the pump is driven at a constant speed at which it delivers a metered amount of fuel the fixed orifice 90 determines the maximum pressure of the delivered fuel. If the quantity of fuel pumped per unit of time was changed by adjusting the inlet valve of the pump or the speed of the pump was changed the maximum pressure of the delivered fuel which is determined by this fixed orifice would change proportionately.

Having thus fixed the maximum fuel pressure which the pump is capable of delivering a variable orifice for obtaining a minimum fuel pressure is provided in the valve 88 by means of the valve stem 9| having a V-shaped notch the opening of which with respect to the partition determines the orifice.. This valve stem is adjustable so the orifice thereof may be completely closed or opened to a degree considerably larger than the open the spring loaded valve 92 to pass to the burner assembly and when the pressure ceases to overcome or equalize the spring pressure the valve closes, thereby sharply shutting off the fuel to the burner, preventing smoking.

The heating coils in this structure are coaxially concentric with their fluid paths in series and are mechanically held in spaced relation by means of three angle irons 93 disposed at 120 from one another. This coil structure is exceedingly simple and has been found to be particularly adapted for this use. The principle of these coil structures shown on the drawings ar disclosed in Patent No. 2,111,538.

The burner assembly illustrated in Figs. 1 and 3 is the same and is per se the subject matter of the co-pending application Serial No. 258,201, filed February 24, 1939. The control valve illustrated in each of the three figures is per se the subject matter of the co-pending application Serial No. 258,200, filed February 24, 1939. The disclosure of these applications are considered a part of the present application for the purpose of the invention claimed herein.

For the sake of illustration the employment of liquid fuel such as oil has been shown and described, but it will be understood that in carrying out the principles of this invention, any suitable source of heat energy may be employed such for instance as electricity or fuel of any character.

I claim:

1. The method of producing a spray mixture of liquid and the vapor of a liquid having maximum liquid content which consists in supplying the liquid at a substantially constant rate to a heat ing zone, applying heat to the liquid within the zone to produce the mixture under pressure, and maintaining a substantially constant pressure and producing maximum liquid content in the mixture by varying the intensity of the heat by means of the pressure of the mixture produced.

2. A method of producing a spray mixture of liquid and a vapor of a liquid having maximum liquid content, comprising continuously supplying a constant amount of liquid to a heating zone, heating the liquid to convert a portion thereof into vapor to produce the mixture under pressure, and controlling the pressure of the mixture and producing maximum liquid content in the mixture by varying the intensity of heat in response to variations of pressure.

3. A method of producing a predetermined pressure on a spray mixture composed of liquid and a vapor of a liquid having maximum liquid content, comprising continuously supplying a constant amount of liquid to a heating zone, heating the liquid to convert a portion thereof into vapor to produce the mixture under pressure, maintaining the pressure of the mixture substantially constant and producing maximum liquid content in the mixture by varying the intensity of the heat in response to variations of pressure.

4. In apparatus for producing a spray mixture of a liquid and a vapor of a liquid having maximum liquid content, the combination of means for supplying liquid to the apparatus at a substantially constant rate, means for applying heat to the liquid, and valvular means actuated by the pressure of the mixture in the apparatus for varying the supply of heat to the liquid to produce maximum liquid content in the mixture.

5. In apparatus for producing a spray mixture of liquid and a vapor of a liquid having maximum liquid content, the combination of means for supplying liquid to the apparatus at a substantially constant rate, means for applying heat to the liquid, mechanism for varying the supply .of heat to the apparatus, and means responsive to the pressure of the mixture in the apparatus .for actuating said mechanism to maintain maximum liquid content in the mixture under a predetermined pressure in the apparatus.

6. In apparatus for producing a spray mixture of liquid and a vapor of a liquid having maximum liquid content, the combination of means for continuously supplying a constant amount of liquid to the apparatus, means for heating said liquid to convert a portion thereof into vapor to produce the mixture under pressure, and means interposed in said heating means and responsive to the pressure of the mixture for varying the intensity of the heat applied whereby to maintain maximum liquid content and a constant pressure on said mixture.

'7. In apparatus for producing a spray mixture of liquid and a vapor of a liquid having maximum liquid content, the combination of means for continuously supplying a constant amount of liquid to the apparatus, means for heating said liquid to convert a portion thereof into vapor to produce the mixture under pressure, and unitary means responsive to the normal pressure of the mixture for varying the intensity of the heat to produce maximum liquid content and responsive to abnormal pressure to discontinue the application of heat.

8. In apparatus for producing a spray mixture of liquid and a vapor of a liquid having maximum liquid content, the combination of means for continuously supplying a constant amount of liquid to the apparatus, means for heating said liquid to convert a portion thereof into vapor to produce the mixture under pressure, and unitary means responsive to the normal pressure of the mixture for varying the intensity of the heat to produce maximum liquid content and responsive to abnormal pressure to discontinue the application of heat, said pressure responsive means restoring the supply of heat to the apparatus when normal pressure is restored therein.

9. In apparatus for producing a spray mixture of liquid and a vapor of a liquid having maximum liquid content, the combination of means for continuously supplying a constant amount of liquid to the apparatus, means for heating said liquid to convert a portion thereof into vapor to produce the mixture under pressure, and unitary means responsive to normal pressure of the mixture for varying the heat to produce maximum liquid content applied and responsive to abhor mal pressure of the mixture for discontinuing the supply of heat and liquid to the apparatus in sequence.

10. In apparatus for producing a spray mixture of liquid and a vapor of a liquid having maximum liquid content, the combination of means for continuously supplying a constant amount of liquid to the apparatus, means for heating said liquid to convert a portion thereof into vapor to produce the mixture under pressure, and unitary means responsive to normal pressure of the mix ture for varying the heat to produce maximum liquid content applied and responsive to abnormal pressure of the mixture for discontinuing the supply of heat and liquid to the apparatus in sequence, said pressure responsive means being arranged to restore the supply oi liquid and heat in sequence when normal pressure is restored therein.

11. In apparatus for producing a spray mixture of liquid and a vapor of a liquid having maximum liquid content, the combination of means for continuously supplying a constant amount of liquid to the apparatus, means for heating said liquid to convert a portion thereof into vapor to produce the mixture under pressure, and unitary means responsive to the pressure of the mixture and actuated by normal pressure to vary the intensity of the heat to produce maximum liquid content and actuated by a greater pressure to discontinue the supply of heat to the apparatus and actuated by an excess pressure to discontinue the supply of liquid to the apparatus.

12. In apparatus for producing a spray mixture 'of liquid and a vapor of a liquid having maximum liquid content, the combination of means for continuously supplying a constant amount of liquid to the apparatus, means for heating said liquid to convert a portion thereof into vapor to produce the mixture under pressure, and unitary means responsive to excessive pressure of the mixture for successively discontinuing the supply of heat and liquid to the apparatus and for successively restoring the supply of liquid and heat when the mixture is restored to normal pressure.

13. In apparatus for producing a spray mixture of liquid and a vapor of a liquid having maximum liquid content, the combination of means for continuously supplying a constant amount of liquid to the apparatus, means for heating said liquid to convert a portion thereof into vapor to produce the mixture under pressure, means responsive to the normal pressure of the mixture for varying the intensity of the heat to maintain maximum liquid content in the mixture, and valvular means for controlling the discharge of said spray, said pressure responsive means successively discontinuing the supply of heat and liquid to the apparatus when said valvular means is closed.

14. In apparatus for producing a spray mixture of liquid and a vapor of a liquid having maximum liquid content, the combination of means for continuously supplying a constant amount of liquidto the apparatus, means for heating said liquid to convert a portion thereof into vapor to produce the mixture under pressure, means responsive to the normal pressure 01 the mixture for varying the intensity of the heat to maintain maximum liquid content in the mixture and valvular means for controlling the discharge of said spray, said pressure responsive means successively discontinuing the supply 01 heat and liquid to the apparatus when said valvular means is closed and successively restoring the supply of liquid and heat when said valvular means is opened.

l5. A method of producing a spray mixture oi liquid and the vapor 01' a liquid having maximum liquid content comprising continuously supplying a constant amount of liquid to a heating zone heating the liquid to convert a portion thereoi into vapor to produce a mixture under pressure and maintaining maximum liquid content in the mixture by varying the intensity of the heat it response to the pressure of the mixture.

FRANK W. OFELDT.

CERTIFICATE OF conREcTI'om Patent 1%. g-52a9,67h. July-111., 19!;2, I

' mm: w. ommr.

fit is hereby certified that error appears in the printed specification 6f the above numbered patent requiring correctionas follows: Page 7,, rirat qoJumn, lines 23 and 56, claims 9 and 10, strike out the word "applied." and insert the same after "heat" inline: 2 and 55, respectively, same claims; and that the said Letter: Petent ehduldbe reed with this correction therein that the ean e may confom to the record or the case in-the Pertent ofiice.

Sigfied and sealed. this 25th day of August, A. D. 1911.2.

Henry Van Aradale, 

